22 
NATURE 
[ Vov. 4, 1869 
spontaneous motions of particles of matter, whether in 
the state of gas or in the liquid state. 
It was known that 1 part by weight of hydrogen occupies 
the same volume as 16 parts by weight of oxygen when 
measured at like temperature, and under like pressure. 
Chemical investigations prove that these equal volumes 
of the two gases contain the same number of atoms. We 
also know that the atoms in such a gas are in rapid motion, 
and resist the pressure to which the gas is at any particu- 
lar time exposed, by striking against the surface which 
presses them together with force equal to that which presses 
them together. 
Thus a given volume of hydrogen is maintained against 
the atmospheric pressure by an energy of atomic motion, 
equal to that of the same volume of oxygen. Each atom 
of hydrogen accordingly exerts a mechanical energy equal 
to that of each atom of oxygen ; but we have seen that 
the hydrogen atom is much lighter than the oxygen atom, 
and accordingly it must move with much greater velocity 
than the oxygen atom. 
Now Graham allowed hydrogen to escape through a 
very small hole in a plate of platinum ; and allowed oxygen 
to escape under similar circumstances. He found that 
each hydrogen atom moves out four times as fast as each 
oxygen atom. His experiments were so arranged as to 
enable him to measure the relative velocities of certain 
motions of the atoms—motions not imparted to them by 
any peculiar or unnatural conditions, but belonging to 
them of necessity in their natural state. He found, 
moreover, that heat increases the velocity of these atomic 
motions, whilst increasing the force with which a given 
weight of the gas resists the atmospheric pressure. 
The study of the condensation of gases by solids, and 
the combination of soluble compounds with membranes 
led him to discoveries which are likely to be of great 
value to physiologists in explaining processes of absorption 
and secretion. 
Thus he found that oxygen is absorbed to a greater 
extent than nitrogen by caoutchouc, and that when a bag 
made of a thin membrane of this substance is exhausted 
by means of a good air-pump, the oxygen and nitrogen 
diffuse through it (probably as condensed liquids), and 
evaporate inside the bag in different proportions from 
those in which they are present in air; the oxygen rising 
to over 40 per cent. of the diffused air. Again, a mixture of 
hydrogen and oxygen was separated almost completely by 
the action of palladium, which condensed the hydrogen in 
very large quantity, and the oxygen very slightly. 
Perhaps the most remarkable substances discovered in 
the course of his experiments on diffusion,'were the soluble 
modifications of tungstic and molybdic acids, ferric oxide, 
&c.,and the process by which these bodies were obtained 
was, perhaps, the most instructive part of the result ; 
proving, as it does, that in their salts, these bodies have 
properties different from those which they normally 
possess in the free state ; and retain them when the other 
constituent is removed by a sufficiently gentle process. 
Another remarkable fact which bears cn a most important 
theory, is the separation effected by Graham of potassic 
hydrate and hydric sulphate, by diffusion of potassic sul- 
phate in aqueous solution—a fact which requires us to 
admit that the solution of the salt in water contains those 
products mixed with one another; just as much as the 
experiment of diffusing air through a porous clay pipe, 
and getting its constituent in a different proportion from 
that of the original air, proved that air is a mixture and 
not a compound of the two gases. 
In his later researches, Graham was assisted by Mr. 
W. C. Roberts, and cordially acknowledged the zeal 
and efficiency displayed by that able young chemist. 
Graham’s scientific influence extended beyond his re- 
searches ; for, on the one hand, his lectures for 18 years at 
University College were remarkable for logical accuracy 
and clearness of exposition, and were highly valued by 
those who had the privilege of hearing them. On the 
other hand, his “ Elements of Chemistry” is a masterly 
exposition of the best known facts of the science and of 
chemical physics. It was translated into German, and 
afforded at that time the most philosophical account of 
the working and theory of the galvanic battery. 
In many of his ideas Graham was in advance of his 
contemporaries, and it might be difficult to find a chemist 
who has dealt more cautiously with general questions and 
delicate experimental operations,—or one whose results, in 
each direction in which he has worked, may more safely 
be expected to stand the test of future investigations. 
A. W. WILLIAMSON 
THE MEETING OF GERMAN NATURALISTS 
AND PHYSICIANS AT INNSBRUCK, TYROL 
ROM the 18th to the 24th of September last the little 
town of Innsbruck wore an air of unwonted bustle 
and excitement. Its population, already augmented by 
the usual throng of summer tourists, was swelled by the 
advent of somewhere about 800 additional visitors—pro- 
fessors, doctors, directors, men of all sciences, often with 
their wives and daughters, who had come from all parts 
of Germany to attend the forty-third Meeting of the 
German Naturalists and Physicians. These meetings 
resemble those of our own British Association, though 
they differ in several very characteristic respects. One of 
the first contrasts to strike an Englishman is the entire 
absence of private hospitality. Everybody, so far as we 
can learn, is in private lodgings or in a hotel; and there 
are no such things as dinner-parties. Although our own 
customs in these respects are certainly very pleasant, there 
can be no doubt that the German fashion leaves the 
visitors more freedom, and allows them much more oppor- 
tunity of seeing and talking with the friends they most 
wish to meet. With us it is no easy matter to get together 
a party of chemists, or geologists, or physiologists, to hold 
a social gathering after the labours of the sections are 
over. We are all either staying with friends, or invited to 
dinner, or engaged in some way. But at the German 
mectings such social reunions are one of the distinguishing 
features. One o'clock in the day brings with it the 
necessity for dining, and numerous dinner parties are im- 
provised there and then ; friends of like tastes, who have 
not met perhaps for a year before, adjourn to a vestaura- 
tion or kaffée-haus, and while eating the meal have a 
pleasant opportunity of comparing notes, and discussing 
questions which have in the interval arisen, 
Another feature of contrast is in the length of time 
devoted to the sitting of the sections. At the British 
Association the sections open their sittings at eleven in the 
forenoon ; and the work goes on steadily all day without 
intermission till four or five o’clock in the afternoon. 
But,in Germany, the sittings commence sometimes as early 
as 8 A.M., and are frequently over by ten or eleven o'clock, 
leaving the rest of the day for some short after-dinner 
excursion, or for general miscellaneous intercourse among 
the members. In fact, the German meetings are designed 
less for the purpose of bringing forward new scientific 
work, than with the view of affording to men of science 
opportunities of becoming personally acquainted with 
each other, and of discussing the value and bearing of 
recent contributions to knowledge. Hence, the papers 
which are brought before the sections, contain, to a large 
extent, outlines, summaries or notices of recent researches, 
and exhibitions of books, maps, memoirs, specimens, 
experiments, &c., which have recently attracted notice. 
In our British Association gatherings, there is probably 
more hard work than in those of our German brethren, 
and IJ daresay there is as much opportunity for sociality 
as suits our national temperament. For our Association 
